The present invention relates generally to intelligent electronic devices, e.g., electronic trip units and protective relays. More specifically, the present invention relates to a method of detecting manual open (trip) or reclose operations in an intelligent electronic device.
Intelligent electronic devices are well known. By way of example, an electronic trip unit (one such intelligent electronic device) typically comprises voltage and current sensors which provide analog signals indicative of the power line signals. The analog signals are converted by an A/D (analog/digital) converter to digital signals which are processed by a microcontroller. The trip unit further includes RAM (random access memory), ROM (read only memory) and EEPROM (electronic erasable programmable read only memory) all of which interface with the microcontroller. The ROM includes trip unit application code, e.g., main functionality firmware, including initializing parameters, and boot code. The EEPROM includes operational parameters for the application code.
These electronic trip units have included a feature to count the number of trips by category, e.g., instantaneous, short time, long time, ground fault, or manual. However, not all manual trips are counted.
Manual trips are initiated via either remotely issued commands, or locally issued commands. Remotely issued commands are received as a network command by the trip unit and then executed. Locally issued commands are commands to open or close the breaker that are not processed by the trip unit, e.g., when an operator turns a breaker handle on or off manually, pushes a trip or reclose button or a trip or reclose signal is received via an auxiliary contact input to the breaker. Locally issued commands are not easily detected and therefore the resulting manual operations are not counted. Being able to count all breaker operations whether manual or automatic, locally or remotely generated is required to properly assess breaker contact wear.